1. Field of the Invention
The present invention relates to a method of monitoring the core body temperature of an animal, and, more particularly, to a method of monitoring the core body temperature of a ruminant animal using an ingestible bolus.
2. Description of the Related Art
It is known to transmit a message in the form of an encoded data packet from a bolus placed within the stomach of a ruminant animal to a remote receiver unit in the form of a stationary base unit or a portable hand-held unit. For example, U.S. patent application Ser. No. 08/918,607 the parent application, describes a system for remotely monitoring a temperature sensed within the stomach of a cow. Such a system is a step forward in the art and allows a user to individually monitor the core body temperature of a plurality of cows in a herd.
Certain physiological states of a cow cause the core body temperature of the cow to vary somewhat relative to a normal core body temperature. For example, several hours before a cow is in standing heat and most likely to conceive, the core body temperature of the cow rises. The core body temperature of a cow may rise, e.g., approximately 0.5.degree. F. about 12 hours before the cow is in standing heat. Additionally, the core body temperature of a cow may rise when the cow is sick, or when the cow is under heat stress associated with very hot ambient conditions. Conversely, the core body temperature of a cow drops shortly before the cow delivers a calf, when the cow is experiencing hypothermia, or when the cow is dead. The core body temperature of the cow is thus an indicator of several different physiological states.
One problem with utilizing an ingestible bolus to determine a core body temperature based upon a sensed temperature within the stomach of the cow is that the cow drinks quite a few times during the course of a day (e.g., 10 to 12 times a day) and ingests a relatively large quantity of water each day. The temperature of the water is, of course, typically much cooler than the core body temperature of the cow. Thus, each time the cow drinks the temperature sensed within the stomach plummets very fast dependent upon the amount and temperature of the water ingested. The temperature data which is received by the remote receiver unit thus varies over a relatively large range.
What is needed in the art is a method of analyzing temperature data associated with temperatures sensed within the stomach of a ruminant animal and a method of displaying the data or alerting the user of a physiological state or a physiological change of the ruminant animal.